This invention relates to a new and distinct cultivar of Calibrachoa plant, hereinafter referred to by the name `Colorburst Rose`. `Colorburst Rose` is a new variety of Calibrachoa plant having a decumbent and compact habit. The plant grows vigorously and makes an excellent hanging basket. The invention's flowers are funnel shaped with five-fissured limbs, and a slight indent on each petal. The flowers are single with a diameter 2.8-3.5 cm when fully open. The petals are red-purple (RHS 74B) with a pale greenish yellow corolla throat (RHS 9A). The plant is very resistant to rain, heat and drought. The plant grows and flowers best under low soil pH conditions (pH 5-6). Typically, flowers will stay open all day and night.
Classification of the current Petunia and Calibrachoa species is still in progress. The genus Petunia was originally established in 1803 by A. L. Jussieu, who described both P. parviflora and P. nyctaginifloa as type species. Using a non-horticultural system that selected the first mentioned species as the type species (lectotype), N. L. Britton and H. A. Brown declared P. parviflora as the type species for Petunia in 1913. During the 1980's and 1990, H. J. Wijsman published a series of articles regarding the ancestry of P. hybrida, the Garden Petunia, and the inter-relationship of several species classified as Petunia. These studies revealed that P. hybrida and its ancestrial species, P. nyctaginiflora (=P. axillaris) and P. violacea (=P. integrifolia), possessed 14 pairs of chromosomes while several other species, including P. parviflora, possessed 18 pairs of chromosomes. Since P. parviiflora was the lectotype species for the Petunia genus, Wijsman and J. H. deJong proposed transferring the 14 chromosome species to the genus Stimoryne. Horticulturists opposed reclassifying the Garden Petunia and in 1986, Wijsman proposed the alternative of making P. nyctaginiflora the lectotype species for Petunia and transferring the 18 chromosome species to another genus. The I.N.G. Committee adopted this proposal. By 1990 Wijsman had transferred several species, including P. parviflora (=C. parviflora) to Calibrachoa, originally established by Llave and Lexarza in 1825. Calibrachoa parviflora (=C. mexicana la Lave & Lexarza) is now the type species for the genus Calibrachoa.
As mentioned above, the classification of the current Petunia and Calibrachoa species is still in progress. New species are also being identified. Consequently a proper description has not been written for the Calibrachoa genus. Calibrachoa can, however, be distinguished from Petunia based on the higher chromosome number, chromosome morphology, plant branching habit and type of flower bud estivation. Whereas Petunia species bear a flower peduncle and one new stem from a node, Calibrachoa bear a flower peduncle and three stems. Petunia species have a cochlear corolla bud, a single outermost petal covers the other four, radially folded and terminally contorted petals. Calibrachoa flower buds are flat with all five petals linearly folded and the two lower petals forming a cover around the three other petals and fused together.
Asexual reproduction of `Colorburst Rose` Calibrachoa originated from a hybridization made in 1996 in Kakegawa, Japan. The female parent was a cross between a bright purple-rose flowered, decumbent habit commercial variety named `Liricashower Rose` (U.S. Plant Pat. No. 9,884) and breeder code C-13. Variety C-13 originated from a commercial market in South America. A single plant from this cross was then backcrossed to `Liricashower Rose`. The initial cross-pollination was made in June, 1995. This F.sub.1 seed was sown in February, 1996 and yielded 20 plants. From these 20 plants, one plant was selected and, during the summer of 1996, `Liricashower Rose` was crossed to it to produce BC.sub.1 seed. In August, 1996 the BC.sub.1 seed was sown and yielded 50 plants. In December, 1996, five plants from these 50 plants were selected and intercrossed in a diallele pattern to produce a diiallele derived BC2 population. In February, 1997 plants from the diallele derived BC2 population were selfed and the selfed seed produced from these plants was sown and yielded 50 plants. From these 50 plants, five plant lines were selected. In August, 1997 the five selected plant lines were vegetatively propagated and tested for easy reproducibility and stability of traits. One of these five plant lines was hence selected for vigorous growth, decumbent habit and bright pink flower color. In December, 1997 cuttings of this plant line were sent to California. During the spring and summer of 1998, plants were grown under the direction and supervision of the inventors for evaluation of stability of the line's desired traits. Plants were evaluated in hanging pots Salinas, Calif., and in the field in Kakegawa, Japan.
The invention, `Colorburst Rose` Calibrachoa, was determined by the inventors to have the characteristics, as herein described, firmly fixed. Plants were grown in plastic pots containing a peat moss-based media. The media pH was maintained between 5.0 and 6.0. Plants were grown under full sunlight in a greenhouse. The media was kept moist by overhead irrigation. A balanced fertilizer containing 20% nitrogen, 20% phosphorous and 20% potassium was applied three times per week through irrigation. The air temperatures ranged from 16.degree. C. to 27.degree. C. during the day and 13.degree. C. to 18.degree. C. at night.
Plants can be finished to full bloom in a variety of containers, including 10, 15, 20 and 41 cm diameter pots. The traits were taken from plants grown in a 41 cm diameter hanging basket with a maturity of 5 months. Two generations of successive propagation were performed between the final selection and collection of traits listed herein.
The new variety is distinguished from other Calibrachoa plants by its flower color, limited branching and vigorous growth.
The closest commercial cultivar to this new variety that we are aware of is the petunia-like plant named `Million Bells Trailing Pink`. The distinguishing characteristics which differentiate `Colorburst Rose` from `Million Bells Trailing Pink` are:
`Colorburst Rose` `Million Bells Trailing Pink` Flower Color: Bright pink Bright bluish pink Flower Size: 2.8-3.5 cm Smaller Flower Throat Color: Pale greenish yellow Light greenish yellow with pink veins Growth Rate: Very vigorous Low vigor